The only option to achieve permanent normoglycemia in diabetic patients is a renewal of the β-cells, either by transplantation of segmental/whole pancreas or isolated islets of Langerhans. Transplantation of isolated islets is considerably less successful compared to whole pancreas transplantation. The immunological barrier, the underlying autoimmune disease and the immunosuppressive drugs used, are the same in both types of transplantation. Thus, there is no obvious immunological explanation as to why transplantation of whole pancreas is more successful than islet transplantation.
If, however, the problems related to the unsuccessful outcome of transplantation of islets were identified and a technical and practical solution was developed, obvious benefits for the patients would be created implying interesting commercial opportunities.
The prior art in this field is largely confined to measures aiming at reducing immunological reactions. WO 9711607 describes transplantation of microencapsulated insulin producing cells as a means of protecting the cells from immunological reactions and/or combined with treating the recipient with a substance that would inhibit an immune-system costimulation. WO 9105855 describes transplantation of islets of animal origin and that the animal tissue should be modified to contain homologous complement restriction factors. DE 19623 440 A 1 describes methods for encapsulation of islets and points out that the artificial encapsulation material may induce platelet activation, coagulation and complement activation, and therefore the encapsulation material should be modified to allow release of inhibiting substances as e.g., heparin, hirudin or Marcumar. U.S. Pat. No. 5,635,178 is not related to transplantation of islets but describes monoclonal antibodies having inhibitory activity towards the terminal complex of complement and that such antibodies can be used to reduce activation of platelets and endothelial cells.
It is evident for those skilled in the art that measures aiming at inhibiting immunological reactions in connection with transplantation of islets regardless of being allogenic or xenogenic have not lead to a satisfactory result in respect of clinical outcome.